Systems

A system is an assembly of interacting components, which affect and are affected by the behaviour of others.

Thus a system is composed of a set of at least two elements and a relation that holds between each of its elements and at least one other element in the set. Each of a system’s elements is connected to every other element, directly or indirectly.1

It is very common in systems thinking to draw lines or arrows between the components to show the relationships, and this can be a powerful aid to thinking and acting. For example, below is a diagram relating to flood containment policy.

Geomorphologist Robert Wasson,
commenting on the orange loop in this diagram, writes:

If you take the levees-only policy of dealing with flood containment on rivers, you have flood losses at the top, which are largely economic losses; this produces public pressure for action, which produces levee construction or enlargement of levees in many places, including Australia. … Levee construction actually increases river height when the river goes over-bank, so the flooding actually is worse as a result of the levees a paradoxical result. Probability of disastrous flood goes up; the actual hazard goes up; the actual risk goes up; the flood losses actually go up as a result of levee construction. This is a positive feedback loop. 2